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aircraft
flew below 500 ft it was exempt from FAA regulations. Using the developed
remote sensing system, data obtained from an altitude of 30 m provided the spatial
resolution of 20 m of land area.
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2.3 Microwave Radiometry and Remote Sensing
of the Environment
Microwave radiometry, or passive microwave remote sensing, is one of the radio-
physical methods used for remote observations of the environment. It is based on
measurements of the natural electromagnetic radiation of objects in the millimeter
to decimeter range of wavelengths. The theoretical aspects of radiophysical mon-
itoring are determined by organizing a measurement procedure in the active or
passive regimes of electromagnetic radiation propagation. An active sensing tech-
nology is based on the radiolocation methods, and a passive one is based on the
background radiation registration. In both cases, theoretical tasks of microwave
monitoring are connected with the study of electromagnetic waves propagation in
the environment and, of course in the
first place, in the atmosphere and near
ionosphere (Kondratyev and Fedchenko 1992; Yakovlev 2001; Yakovlev et al.
2009; Chukhlantsev 2006; Gulyaev et al. 2009; Pavelyev et al. 2010).
In the active regime the talk is about the propagation of electromagnetic waves
of various ranges from the emitter to the receiver. Two cases are possible here. In
the
first case, the transmitter and receiver have different position in the environment
and the decision about the assessment of the environment parameters is accepted on
the base of registered distortion of transmitted signal. In the second case, the
transmitter and receiver are combined so that estimation of the environment
parameters is made on the base of analysis of the emitted signal absorption and
distortion of received its re
ection. Clearly, the time it takes the signal to propagate
in the environment is the information parameter. An active form of microwave
monitoring is typical for the atmosphere radiotranslusense method.
Basic advantage of microwave remote sensing lies in its largely immune to
clouds, precipitation, smoke, etc. and a capacity to penetrate sand, soil, rock,
vegetation, dry snow, ice, etc. Knowledge of the physical processes associated with
energy emission at microwave range gives a possibility to calculate a variety
of surface and atmospheric parameters, including air temperature, sea surface
temperature, salinity, soil moisture, sea ice, precipitation, the total amount of water
vapor and the total amount of liquid water in the atmospheric column directly above
or below the instrument.
The passive methods of microwave monitoring are based on SHF-radiometry. The
existence of resonance absorption
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fields in SHF range allows remote reconstruction
of meteorological atmosphere parameters such as the vertical pro
les of temperature,
humidity, total water vapor mass, water storage in the clouds, and precipitation
intensity, etc. The possibility to receive data not only about the properties of water and
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